Electric switch mechanism



April 1957 H. A. DUVALL ETAL 2,789,169

ELECTRIC SWITCH MECHANISM 4 Sheets-Sheet 2 Filed July 15, 1955 April,1957 H. A. DUVALL ETAL 2,789,169

ELECTRIC swrrcn MECHANISM 4 Shee ts-Sheet 5 r m? M HE; T 7 1 5 z N FiledJuly 13, 1955 .IIIIII April 1957 H. A. DUVALL ETAL 2,789,169

ELECTRIC SWITCH MECHANISM 4 Sheets-Sheet 4 Filed July 15, 1955 7 7 S T ama; W r ,E% to a m d 4 @w/ 1 0 6 ,0 9 -L m .O

United States Patent ELECTRIC SWITCH MECHANISM Harold A. Duvall,Pasadena, and Charles G. Esler,

Arcadia, Calif., assignors to Square D Company, Detroit, Mich acorporation of Michigan Application July 13, 1955, Serial No. 521,696

10 Claims. (Cl. 200-56) This invention relates generally to switchedfuse cabinets and more particularly to the operating, closing andswitching mechanisms of a fused electrical switch.

One object of the invention is a dead front hinged cover switchingdevice for a fuse'panelboard.

Another object of the present invention is a novel overcenter operatingmechanism for an enclosed fused switching device.

A further object of the present'invention is an operating mechanismmounted on a hinged cover for an enclosed switching device adapted to beincorporated into a fuse panelboard in which the movable contacts of theswitching device remain in the body of the device and theoperating'mechanism and external operator are movable with the hingedcover.

A further object of the present invention is a plug-in type distributiondevice including fuse holding means and switching means for opening andclosing circuits" through the device and in which the fuse holding meansand the switching means are contained within the device enclosure andthe operating mechanism and the external operator therefor are movablewith relation thereto with a hinged cover for the enclosure.

A further object of the present invention is a switching device adaptedto be incorporated into a fuse panelboard having movable bridgingcontacts and external operating mechanism in which the bridging contactsare rectilinearly movable within the device and the external operatingmechanism is rotatable to effect the contact movement and in which anovercenter mechanism is provided intermediate the operator and'thecontacts for accomplishing the conversion of movements.

A further object of the present invention is the provision of anoperating mechanism with a'reversible external operator for an enclosedswitching device adapted to be incorporated into a fuse panelboardwhereby the device may be oriented in either of two directions and theexternal operator alone may be reversed with respect to the device so asto maintain a uniformity of appearance of several devices regardlessoforientation when incorporated into a panelboard.

Other objects and features of the invention will be readily apparent tothose skilled in the art from the following specification and appendeddrawings illustrating a certain preferred embodiment of the invention inwhich:

Figure 1 is a front elevational view of the switching device of thepresent invention shown in one of two alternative alignments.

Figure 2 is a sectional View taken along the lines 11-11 of Figure 1.

Figure 3 is a sectional View taken along the lines iii-III of Figure 1.

Figure 4 is a sectional view taken along the lines 1V-1V of Figure 3.

Figure 5 is an elevation and partial section'view of the operatingmechanism of the present invention taken along the lines VV of Figure 3.

Figure 6 is a front elevational view of the switching device of thepresent invention with the device positioned in a second of twoalternative positions and with the external 0 erating mechanism shown inits reversed position;

Referring'now to Figure l of the drawings illustrating the switchingdevice of the present invention shown gen erally at it} and comprising afolded sheet metal enclosure 12' and cover 14 hinged at 16 to an endplate 18 secured to the side enclosure 12 at one end thereof. The endplate 18 is provided with an extending flange 20 and a similar flange 22is provided at the opposite end of the device to provide'niounting areasfor the positioning of the device in a distribution panelboard as shownin the copending application of Ralph H. Kingdon, S. N. 555,- 639, filedDecember 27, 1955, for Electrical Panelboard, and assigned to this sameassignee. Generally centrally of the pivoted cover 14 is an externaloperator 24 rotatably supported on an escutcheon plate 26 and adapted topass through the cover 14, as will be described hereinafter, to operatethe operating mechanism of the switching, device of the presentinvention. The escutcheon plate 26 is secured to the cover 14 bysuitable screws 25 and, as will be described hereinafter, is reversibleon the cover 14 to allow the device and the handle to be aligned ineither of the two alternative positions. A conventional spring biasedhook lock 27 is secured to the inside side wall of the enclosure 12, ina manner not herein illustrated, and'passes through a slot 28 in thecover 14 to provide hooking and locking means for the cover in itsclosed position. The cover is also provided with a circular cutout hole29 through which access may be had to a second cover locking mechanism,to be more fully described hereinafter, to permit opening movement ofthe cover while-the switching device is retained in its on position.

As illustrated in Figures 2, 3 and 4, the switching device of thepresent invention incorporates an assembly of a plurality of insulatingblocks establishing spaced barriers and operating cutouts within which asuitable plurality of fuses and switching members may be'supported andoperated to accomplish switching and distribution of electrical energythrough the device. The insulating base portions of the deviceconstitute a contact base assembly 30, a contact cover assembly 32, anda fuse base assembly 34. The contact base assembly 36 is supported bysuitable screws 36 and 37 which pass also, respectively, through thefuse base assembly 32 and the contact base cover assembly 34 to securethe insulating devices to a bottom plate 38 fixed by suitable screws 39passing through the plate 38 and cooperating with a threaded bent overportion of bracket 40 suitably secured to the side plates 12 of thedevice as by means such as welding.

Referring now to Figure 2 wherein the contact base assembly 30 is shownas provided with a plurality of parallel recesses 42, and 46, separatedby insulating barriers 43 and 4S, and establishing parallel operatingchannels for a like plurality of bridging contacts 47, 48 and 49 whichare respectively secured to insulating blocks 51, 52 and 53'shown inFigure 4 by suitable screws such as 54. To the opposite ends of theinsulating blocks 51, 52 and 53, a pair of operating hooks 55 aresecured as by' molding with the blocks 51, 52 and 53 so as to bepermanently and securely fixed thereto. Each of the bridging contacts47, 48 and 49 is provided with extending legs'56 and 57 which areindividually adapted to cooperate with spring jaw clips 58' and 59 so asto electrically bridge the contacts and complete a circuit therethroughas will be more completely described hereinafter.

An operating bail 60' extends through the cutout slots maintained. Theinterior surface of the contact base 7 assembly 30 is cut out at theedges at 67 and the central insulating barriers 43 and 45 are terminatedgenerally centrally of the length of the contact base assembly toestablish a generally arcuate operating area for the bail 60 and theside levers 64.

To the exterior of the switching device and to the outer base portion ofthe contact base assembly 30, a suitable plurality of spring jawconnectors 71 are secured with their associated bus connectors 72 ofvarying lengths so that the connectors 71'are disposed for theaccommodation of isolated phases of a multiphase source and to one endof these conductors 72 folded over terminal straps 74 are secured as bystuds 76. The folded over terminal straps 74 extend inwardly into thecontact base assembly with a leg 78 at the extreme end of which aresecured as by suitable rivets and conventional biasing members thespring jawed contacts 59.

Supported on the inside surface of the contact base assembly 30 is thepreviously mentioned contact base cover assembly 32 having an insulatingbase portion 80 and separating barriers 82. Between the insulatingbarriers 82 are supported a suitable plurality of spring fuse clips 84on folded terminal conductors 85 secured to the base 80 of the contactbase cover assembly by suitable screws at 86. Also secured to theterminal conductor 85 byscrews 86 is an extending folded over terminalstrap 87 passing through the base of the contact base cover assembly 32and into the aligned recess in the contact base assembly 30 and at theextended end thereof there is secured thereto, as by suitable rivets andbiasing springs the spring jaw clips 58, previously mentioned.

At the opposite end of the contact base assembly and to the interiorsurface thereof, the previously mentioned fuse base assembly 34 issecured as by the previously mentioned screw 36 and a similar screw 35at the opposite end thereof. The fuse base assembly comprises aninsulating base 90 and spacing insulation barriers 92 between which aresupported a suitable plurality of spring fuse clips 94 on terminalstraps 95 secured to the insulating base 90 by suitable screws 96. Theremay also be secured to the spring jaw fuse clips 94 and terminal strap95 a suitable plurality of lugs 97 to which may be secured theconductors leading to the load devices to be controlled by the fusedswitching device of the present invention. It is to be understood thatthe end or the side walls of the enclosure will be provided with cutoutor knockout openings through which the conductors to the load may pass.

To the inner surface of the hinged cover 14 of the switching device ofthe present invention the operating mechanism for the movable bridgingcontacts 47, 48 and '49, just described, is supported so that it may bepivotally moved with the cover to permit access to the interiormechanism of the device. The operating mechanism for the bridgingcontacts constitutes an external manual operator 24 and the internalovercenter snap-acting operating mechanism as shown in Figure 5 andgenerally designated 101. The external operator 24 is provided with acentral shaft 102 extending through the escutcheon plate 26 andterminating inside of the hinged cover 14.

to the interior surface of the cover 14, the pan 107 being secured as byscrews 111 to the channels 109. Slidably supported within the pan 107and between the pan and the cover 14 is a slide member 112 having acentral cutout portion at 113 and folded over cam riders 114 at theedges of the cutout 113. The cam roller on the cam member 103 moved bythe operator 24 is positioned within the cutout 113 and is adapted tooperate against the cam surface 114 to move the slide member 112 betweenthe pan 107 and the cover 14 along the cutouts provided in the channelmembers 109. The slide member 112 is provided with an extension 115having secured thereto by suitable means a bearing pin 116 about which apair of spring guides 117 and 118 are positioned and held in place bymeans such as a cotter pin 119. Surrounding the spring guides 117 and118 are a pair of springs 121 operating against shoulders of the springguides near their pivoted ends and at the opposite ends against turnedup shoulders 122 of a pair of pivoted toggle brackets 123 pivotallysupported on the pan 107 by peened over rivets 124 so as to be rotatablysupported for toggling action of the over-center spring mechanism. Itshould be readily apparent that as the cam roller 105 is arcuately movedby the external operator 24 in contacting the cam surfaces 114 toreciprocate the slide member 112 between its two limits, as defined bythe cutout channels in the channel members 109 at limits at one end andat the other end a limit by rib 145, that the extending portion willmove through the overcenter position for the springs 121 so that, havingpassed through the overcenter position, the springs 121 will exert theirbiasing force to maintain the slide member 112 in an oppositely limitedposition against limits 110 from that indicated in Figure 5.

An insulation barrier 124 is positioned between the operating mechanism101 and the contact cover assembly 32 and the contact base coverassembly 34 and is supported by suitable rivets 125 on the inner surfaceof the pan 107.

The reciprocating movement of the slide member 112 is transmitted to theoperating lever 64 for the bridging contacts 47, 48 and 49 through theengagement of the operating end of the lever 64 in cutout slots 131 ofside extensions 132 of the slide member 112. As the slide member 112 ismoved between its limits within the channel 109 and between the pan 107and the cover 14, the operating lever 64 is reciprocated to transferreciprv eating motion to the bridging contacts 47, 43 and 49 through itsengagement with the hook shaped brackets 55. This reciprocating motionis effected with a snap-action due to the overcenter operation of thesprings 121 to effect a both rapid and forceful movement of the bridgingcontacts into engagement with the spring contacts 58 and 59 so as tocomplete the circuit from the sources at spring clips 71 through thebridging contacts to the fuse clip 84 and thus through the fusingdevice, not herein shown, but normally positioned between the fuse clips84 and 94 so as to provide at the lugs 97 the necessary energization fora connected load device.

A lever lock mechanism is provided on one side of the enclosure 12adjacent to the operating end 130 of lever 64 for insuring that thebridging contacts 47, 48 and 49 will not accidentally be moved to aposition to bridge the contacts 53 and 59 when the cover 14 is opened.For this purpose a locking lever 68 is pivotally supported on the sideof the enclosure by a suitable rivet in the enc1o sure side as shown at69. The locking lever 68 is spring biased by a resilient spring wire 70operating at one end against the lip of the enclosure side and passesaround the rivet 69 to operate, at its other end, against a notch in thelever so as to normally bias the locking lever 68 in a clockwisedirection as viewed in Figure 3. The lever is further provided with abent over shoulder at 73 aligned for cooperation with an extending arm100 on ensures inside surface of the paniIO'iso that as thecover' isclosed, the armwill engagelthe shoulder 73 torotate the locking lever 68counter-clockwise about the rivet 69 and against the bias of'the spring70.

The end of the locking lever'fi opposite to the shouldered end 73 isadapted to engage a'pressed out stop 75 on the operating lever 64. inits freeunre'stricted position. That is, when'the cover 14 is opened,the locking lever 68 will rotate into aligned position with the stop 75'being limited in its clockwise rotation under the bias of spring 7% bythe engagement of the end of the locking lever near the shoulder 73 withthe lip of the enclosure in this locking-position, the lever 64 maynotbe rotated to slide the bridging contacts '47, 43 and d9 except byrelease of the locking lever With the cover 14 closed, the locking lever63 will be removedfrom locking alignment and the levers 64 may beoperated in their normal fashion.

The operating mechanism for the fused switching device is furtherprovided with acover latching mechanism adjacent to the end of theoperating mechanism which moves away from the sides of the enclosure 12in opening movement of the cover 14. The latching mechanism constitutesa spring biased latch 135 pivotally supported on a rivet 136 on the pan107 for rotatable movement.

The latch 135 is formed into a substantially U shape with i legs 137 and138 disposed respectively adjacent to the cover 14 and the pan 167. Leg133 ofthelatch 135, at its extremity, is formed into a latching surface139, and is disposed for engagement with surface 1410f the end surfaceof the sides of the enclosure 12 so as to latch under the surface l ilandprevent opening'movement of the cover 14. Opposite to the latchingsurface 139, on the leg 13%, a spring guiding shoulder 142 is formedwith a pressed out guide 143 so as to act both asa guide and a shoulderfor a biasing spring 144 acting at one end against the shoulder 1.42 andat the opposite end against a stationary rib 1 55 of the pan 107. Aportion of the rib 1145 is bent over to form a guide 146 for that endfor the biasing spring 144. Under unrestricted operation of the latch135, the spring 144 will bias the latching surface 139 of the latch 135into engaged position with the surface 141 of the enclosure for theswitching device so that with the cover closed and with the latch .139in 'engagement with the surface 141, the cover 14 may not normally beopened. To permit Opening of the cover 1 while the latching surface 139is in engageable position with the latching surface 141, a latch releasemeans is accessible through an opening 29 in the cover 14. Coaxial withthe rivet 136, the leg 137 of the latch 135 is provided with ascrewdriver type accommodating slot 147 which may be engaged by ascrewdriver blade or similar instrument passing through the cover 14.With this accommodation, the cover 14 may be opened even though thelatch 139 is in normal engagement position with the latch surface 141 byinserting a screwdriver or similar instrument through the hole 29 toengage the slot 147 and then rotating the latch 135 to remove thelatching surface 139 from its engagement with the latching surface 141.

Figure illustrates the operating mechanism for the switching device ofthe present invention in its contacts open position, and illustrates theslide 112 in its limited position for this condition. The slide 112 isprovided with an extending arm 151 which, in the position illustrated inFigure 5, extends through a folded over slot in the rib 145 at 152. Theextending arm 151 is aligned to engage the bight portion of the latch135 to rotate the latch in a counter-clockwise direction against thebias of spring 144. to remove the latch end 13? from its engagedposition with the latching surface 141 of the end barrier of the sideplates 22 of the enclosure, so that when the switch mechanism is in theopen circuit or off condition, the cover 14 may be readily opened withrelease of the conventional latch 27 from engagement with the slot 28 asillustrated in Figure 1 of the drawings.

ltishouldbeeapparent that with the coverin the open sposition not hereinillustrated, the external operator 24 'may be manipulatedto move theoperating mechanism :to either its on or off positiom'however, when thecover is-returned-to-its enclosing position, the operatingmechanism=mustbe returnedtoithe position of the internalIswitchingmechanisms as established by the position of theextending :arm 130 of the switch lever 64. If the operating mechanism isin a non-conforming position with extending'arm 130-of theoperatinglever 64, the covermay not :be closed due to the restrictingnon-alignment of.theasidexextensions 132 of the slide 112 with theextending arm130of the operating lever 64.

Figure 6 illustrates the device of the present invention in a reversedmounting position with the escutcheon plate 26 in a reversedpositionwith respect tothe cover 14 of the device. The construction of theopening 113 in the slide member'112andfthe construction of the operatingcam rolleris such that the reversal of the escutcheon plate '26 withcoincident'reversal of operating lever 24 will return the operating camroller 105 to its alignment rality of :theseswitchingdevices areemployed, adjacent or alternate switching devices may be reversed withinthe panelboard topermit distribution of the load conductors to eithersideof the panelboard thereby reducing both the congestedcondition ofwiring gutters and permitting the employmentof narrower gutters bythedistribution of the load conductors. The-reversal of the unit withinthe panelboard with coincident reversal of the escutcheon plate andoperating handle maintains the systematic alignmentofatheescutcheonplates with merely the reversal .of the operating handle fromone side to the other of the cover. If alternate or adjacent units arereversed, the nameplate andload designations generally affixed to theescutcheon plate willbemaintained in their proper alignment and theadjacent operating handles will merely have reversed alignment for'theiroil and on conditions.

The operation 'of'the switching device of the present invention isconsidered to be readily apparent from the description and operativeanalysis of the various coirponents of the device'hereinbeforepresented. It should beunderstoodthat the device illustrated in thedrawings is merely descriptive of one of many varieties dictated by bothvoltage and current ratings for the device illustrated'and while onlyonepreferred embodiment of the invention -has been illustrated herein,it should be under stood that'further variations will be readilyapparent to those :skilled .inthe art and that the invention hereinshouldi'not be 'limitedto'the specific disclosure shown but'should begiven'its broadest possible interpretation withinithe'terms ofthefollowing claims:

"What is claimed is:

1. An. electric switch comprising an enclosure, a hinged cover for saidenclosure, insulating means supported within said enclosure, linecontacts supported within said insulating. means,load contacts supportedwithin said insulating .means, bridging contacts adapted to bridge said'line and load contacts, said bridgingcontacts being supportedwithinsaid enclosure for slidable movement within said insulating means, meanswithinsaid enclosure for slidably moving'saidbridging contacts, andmeans supported .on said coverifor operating said means for movingzsaid'bridging contacts.

2. .An electric switchcomprising an enclosure, a hinged cover for .saidenclosure, insulating means supported r 7 said insulating means,bridging contacts adapted to bridge said line and load contacts, saidbridging contacts being supported within said enclosure for slidablemovement within said insulating means, lever means pivotally supportedon said enclosure for slidably moving said bridging contacts, and snapacting operating means supported on said cover and engageable with saidlever means for eifecting movement of said lever means to move saidbridging contacts.

3. An electric switch comprising an enclosure, a hinged cover. for saidenclosure, insulating means supported within said enclosure, linecontacts supported within said insulating means, load contacts supportedwithin said insulating means, bridging contacts adapted to bridge saidline and load contacts, said bridging contacts being supported Withinsaid enclosure for slidable movement within said insulating means, levermeans pivotally supported on the said enclosure for slidably moving saidbridging contacts, means supported on said cover for effecting movementof said lever means including a member slidably movable contiguous tosaid cover, overcenter spring means biasing said member to either of twoalternative positions and causing movement from one to the other of saidpositions to be with a rapid snap action, and means on said memberengageable with said lever means for effecting movement of said levermeans with a snap action to move said bridging contacts.

4. An electric switch comprising an enclosure, a hinged cover for saidenclosure, insulating means supported within said enclosure, linecontacts supported within said insulating means, load contacts supportedwithin said insulating means, bridging contacts adapted to bridge saidline and load contacts, said bridging contacts being supported withinsaid enclosure for slidable movement within said insulating means, levermeans pivotally supported on said enclosure for slidably moving saidbridging contacts, operating means supported on said cover for saidlever means including channel members fixed to said cover, a pan memberfixed to said channel members, said pan member being spaced from saidcover to provide an operating area therebetween, a slide membersupported by said pan member and slidable between said pan and saidcover in said operating area, overcenter spring means biasing said slidemember to either of two alternative positions and causing movement fromone to the other of said positions to be with a rapid snap action, meanson said slide member engageable with said lever means for effectingmovement of said lever means with a snap action to move said bridgingcontacts, and an external manual operator for maniplating said slidemember.

5. An electric switch comprising an enclosure, a hinged cover for saidenclosure, insulating means supported within said enclosure, linecontacts supported within said insulating means, load contacts supportedwithin said insulating means, bridging contacts adapted to bridge saidline and load contacts, said bridging contacts being supported withinsaid enclosure for slidable movement within said insulating means, levermeans pivotally sup ported on said enclosure for slidably moving saidbridging contacts, operating means supported on said cover for saidlever means including channel members fixed to said cover, a pan memberfixed to said channel members, said pan member being spaced from saidcover to provide an operating area therebetween, a slide membersupported by said pan member and slidable between said pan and saidcover in said operating area, overcenter spring means biasing said slidemember to either of two alternative positions and causing movement fromone to the other of said positions to be with a rapid snap action,portions of said slide member being cut out generally centrally therof,folded edges of said central cut-out defining cam riders on said slide,an external operator, a cam roller fixed to said operator adjacent tothe innersurface of said cover,.said roller .extending into said centralcut-out and being engageable with said cam riders to effect movement ofsaid slide member with manipulation of said external operator, and meanson said slide member engageable with said lever means for effectingmovement of said lever means with a snap action to move said bridgingcontacts.

6. An electric switch comprising an enclosure, a hinged cover for saidenclosure, insulating means supported within said enclosure, linecontacts supported within said insulating means, load contacts supportedwithin said insulating means, bridging contacts adapted to bridge saidline and load contacts, said bridging contacts being supported withinsaid enclosure for slidable movement within said insulating means, levermeans pivotally supported on said enclosure for slidably moving saidbridging contacts, operating means supported on said cover for saidlever means including channel members fixed to said cover, a pan memberfixed to said channel members, said pan member being spaced from saidcover to provide an operating area therebetween, a slide membersupported by said pan member and slidable between said pan and saidcover in said operating area, an overcenter spring means biasing saidslide member to either of two alternative positions and causing movementfrom one to the other of said positions to be with a rapid snap action,means on said slide member engageable with said lever means foreffecting movement of said lever means with a snap action to move saidbridging contacts, means for latching said cover to said enclosure andmeans operated by said slide member for releasing said latch means, andan external manual operator for manipulating said slide member.

7. An electric switch comprising an enclosure, a hinged cover for saidenclosure, insulating means supported within said enclosure, linecontacts supported within said in sulating means, load contactssupported within said insulating means, bridging contacts adapted tobridge said line and load contacts, said bridging contacts beingsupported within said enclosure for slidable movement within saidinsulating means, lever means pivotally supported on said enclosure forslidably moving said bridgin contacts, operating means supported on saidcover, a pan member fixed to said channel members, said pan member beingspaced from said cover to provide an operating area therebetween, aslide member supported by said pan member and slidable between said panand said cover in said operating area, overcenter spring means biasingsaid slide member to either of two alternative positions and causingmovement from one to the other of said positions to be with a rapid snapaction, means on said slide member engageable with said lever means foreffecting movement of said lever means with a snap action to move saidbridging contacts, means for latching said lever means in contacts openposition when said cover is open and means operated by said pan memberfor releasing said latch when said cover is closed, and an externalmanual operator for manipulating said slide member.

8. An electric switch comprising an enclosure, a hinged cover for saldenclosure, insulating members supported within said enclosure, line andload contacts supported within said insulating members and bridgingcontacts supported within said insulating means and adapted to bridgesaid line and load contacts, an operating mechanism for manipulatingsaid bridging contacts into engaged and disengaged position with saidcontacts, an external operator for said operating mechanism, said switchbeing adapted to be supported in either of two alternative orientations,and said external operator being reversible with respect to said switchto maintain a uniformity of alignment thereof regardless of theorientation of said switch.

9. An electric switch comprising an enclosure, a hinged cover for saidenclosure, insulating members supported within said enclosure, line andload contacts supported within said insulating members and bridgingcontacts supported within said insulating means and adapted to bridgesaid line and load contacts, an operating mechanism for manipulatingsaid bridging contacts into engaged and disengaged position with saidcontacts, an external opertor for said operating mechanism, anescutcheon plate on the exterior surface of said cover for supportingsaid operator, said switch being adapted to be supported in either oftwo alternative orientations, and said escutcheon plate being reversiblewith respect to said switch on reversed orientation of said switch tomaintain a uniformity of alignment of said escutcheon plate and externaloperator regardless of orientation of said switch.

10. An electric switch comprising an enclosure, a hinged cover for saidenclosure, insulating means supported within said enclosure, linecontacts supported within said insulating means, load contacts supportedwithin said insulating means, bridging contacts adapted to bridge saidline and load contacts, said bridging contacts being supported withinsaid enclosure for slidable movement within said insulating means, levermeans pivotally supported on said enclosure for slidably moving saidbridging contacts,

10 means supported on said cover for effecting movement of said levermeans including a member slidably movable contiguous to said cover,portions of said member being cut out generally centrally thereof anddefining a rectangular cam area, an external operator, a cam rollerfixed to said operator adjacent to the inner surface of said cover, saidroller extending into said rectangular cam area and being engageabletherewith to effect movement of said slide member with manipulation ofsaid external operator.

References Cited in the tile of this patent UNITED STATES PATENTS1,561,248 Krantz Nov. 10, 1925 2,315,420 Harrington Mar. 30, 19432,536,522 Wilson Jan. 2, 1951 2,674,666 Stieglitz Apr. 6, 1954 2,695,934Wills Nov. 30, 1954 FOREIGN PATENTS 105,187 Australia Sept. 15, 1938

